Elongated connecting elements, such as rods, plates, tethers, wires, cables, and other devices have been implanted along the spinal column and connected between two or more anchors engaged between one or more spinal motion segments. Such connecting elements can provide a rigid construct that resists movement of the spinal motion segment in response to spinal loading or movement of the spinal motion segment by the patient. Other connecting elements can resist loading or movement of the spinal motion segment that creates a tension force on the connecting element; however, the connecting element collapses in response to any compression loading and provides little or no resistance in response to such forces or movement. Still other connecting elements are flexible to permit at least limited spinal motion while providing resistance to loading and motion of the spinal motion segment that is the same in both compression and tension.
While prior connecting elements provide various spinal stabilization options, there remains a need for connecting elements that can provide variable resistance properties to forces and motion in different directions along the spinal motion segment for dynamic stabilization.